1. Field of the Invention
The present invention relates to data transmission in an electronic device. Particularly, the present invention relates to a data transmission method and an electronic device in which a host device and a module carry out the data transmission method.
2. Description of the Related Art
In a digital broadcasting television set and a personal computer, it is necessary to protect the contents from illegal copy. For this purpose, it is general to employ a method of encrypting the contents by use of a specific key, as described in Japanese Laid Open Patent publication (JP-P2004-109177A).
However, even implementation of dedicated hardware and software for encryption, there still remains a risk that the contents are copied and decrypted when a general-purpose bus that is officially standardized is used. In the general-purpose bus, terminal numbers for data transmission and reception are defined. Accordingly, if data transmitted on a line between the terminals related to the data transmission is recorded, the data could be decrypted and copied by trying various decryption methods.
Through the spread of the digital broadcasting television, it would be anticipated that enhancement of contents data protection is indispensable. Thus, electronic devices such as a personal computer, a video recorder, a PDA (Personal Digital Assistance), and a mobile terminal having a function of receiving the contents data are required to have a function of preventing copy of the contents data.
As described above, the copy of the contents data is often carried out by recording a data packet stream flowing through the general-purpose bus. Therefore, one countermeasure is to use a special bus that is not the general-purpose bus. However, this causes heavy loads in terms of development and maintenance of the electronic device.